It's preferable to have it away from other electronic components, but this is almost impossible in todays chassis's.
I have seen a few cars where the receiver is on top of the servo, so presumably they don't have problems with interference etc. It's certainly better than having it near the ESC.
Xray T4'16, T4'14 (Wet Car)
Xray X12 2016
wlrc.co.uk (West London Racing Centre)